Slide 2 What are three stimuli that produce plant responses?
Tropisms, hormones, and Auxin Slide 3 Tropism A Tropism is a
response to a plant toward or away from a stimulus. If a plant
grows toward the stimulus, it is said to show a positive tropism.
If a plant grows away from a stimulus, it shows a negative tropism.
Touch, gravity, and light are three important stimuli that trigger
growth responses, or tropisms, in plants. An example of a stimulus
is when a fly is flying near a Venus Flytrap, the flytraps response
is to munch on the fly. A Venus Flytrap is a Carnivorous Plants.
Slide 4 Hormones and Auxin A, which is produced by a plant, is a
chemical that affects how the plant and develops. One important
plant hormone is called the auxin. (AWK sin) Auxin speeds up the
rate at which a plants cells grow and controls a plants response to
light. When light shrines on one side of a plants stem, auxin
builds up in the shaded side of the stem. The cells on the shaded
side begin to grow faster. The cells on the stems shaded side are
longer than those on its sunny side. The stems bend toward the
light. A hormone, which is produced by a plant, is a chemical that
affects how the plant grows and develops. One important plant
hormone is called the auxin. (AWK sin) Auxin speeds up the rate at
which a plants cells grow and controls a plants response to light.
When light shrines on one side of a plants stem, auxin builds up in
the shaded side of the stem. The cells on the shaded side begin to
grow faster. The cells on the stems shaded side are longer than
those on its sunny side. The stems bend toward the light. Slide 5
Photoperiodism, Critical Night Length, Short-Day Plants, Long-Day
Plants, Day Neutral Plants, and Dormancy Slide 6 photoperiodism The
amount of darkness a plant receives determines the time of
flowering in many plants. A plants response to seasonal changes in
the length of night and day is called photoperiodism. critical
night length, Plants respond differently to the length of nights.
Some plants will only bloom when the nights last a certain length
of time. This length, called the critical night length, is the
number of hours of darkness that determines whether or not a plant
will flower. For example, if a plant has a critical night length of
11 hours, it will flower only when there is over 11 hours of
darkness. Slide 7 Short-day plants flower when the nights are
longer than a critical length. They bloom in fall or winter.
Long-day plants flower when nights are shorter than a critical
length. They bloom in the spring or summer. Day-neutral plants have
a flowering cycle that is not sensitive to periods of light and
dark. They can bloom year-round depending on the weather. Dormancy
is a period when an organisms growth or activity stops. Dormancy
helps plants survive freezing temperatures and the lack of liquid
water. Slide 8 1. What is a plants growth response called? a. Auxin
b. Hormone c. Tropism 2. What are short-day plants? a. When the
nights are shorter than a critical length b. When the nights are
longer than a critical length c. Has a flowering cycle that is not
sensitive to periods of light and dark. 3. Plants responses to
seasonal changes in the length of night and day is a. Critical
night length b. Photoperiodism c. Dormancy Slide 9 4. A _______ is
produced by a plant is a chemical that affects how the plant grows
and develops. a. hormone b. auxin c. tropism 5. One important plant
hormone is named a. dormancy b. tropism c. auxin 6. What are
long-day plants? a. flower when the nights are longer than a
critical length. b. have a flowering cycle that is not sensitive to
periods of light and dark. c. flower when nights are shorter than a
critical length. 7. What is the critical night length? a. a period
when an organisms growth or activity starts. b. when some plants
only bloom for a certain length of time. c. a plants growth
response toward or away from a stimulus. Slide 10 8. Day neutral
plants: a. have a flowering cycle that is not sensitive to periods
of light or dark. b. flower when nights are shorter than a critical
length. c. flower when nights are longer than a critical length. 9.
Dormancy is: a. produced by a plant is a chemical that affects how
a plant grows. b. The period when an organisms growth or activity
stops. c. A plants response to seasonal changes in the length of
night and day. 10. The name of lesson five is: a. Three Stimuli
that produce plant responses b. Plants seasonal changes responses
c. Plant responses and growth
